Method of erecting an offshore structure



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United States Patent Ofifice 3,107,495 Patented Oct. 22, 1963 New JerseyFiled Apr. 29, 1959, Ser. No. 809,838 2 Claims. (Cl. 61-46) Thisinvention pertains to improvements in off-shore oil drillingconstructions and construction methods, and provides for such andrelated applications, drilling platforms and methods of installationembodying novel and unique features which greatly reduce the time andexpense involved while affording a superior type of structure.

In the past decade, commercial exploitation of offshore drilling for oilhas increased enormously. In consequence, improvements in installationmethods, materials and structures for such purposes have receivedincreasing attention.

According to one construct-ion heretofore successfully employed, thedrilling platform comprises a precast rectangular concrete deck frame,mounted at each of its corners on a pair of prestressed concrete, shellpiles, one a plumb or vertical pile and the other 'a batter pile. Thisconstruction has the disadvantage, however, that each pair of thevertical and batter piles must be connected by means of a concrete capwhich is poured in two stages. The first portion of each cap is pouredbefore placement of the concrete deck frame. After the concrete has set,the deck frame is lowered onto the caps, whereupon the second portion ofeach cap is poured to finish off the structure. This is both timeconsuming and expensive.

In accordance with the present invention the drilling platform comprisesa prefabricated superstructure of steel consisting of a skeletalframework of substantial area and depth, trussed against vertical,horizontal and corner-tcorner deflection, and on which is mounted atspaced points about its periphery, a series of upstanding collars ofroughly oval contour in plan view.

The transverse dimensions of these collars are such, as in onemodification, to enter a batter pile therein, or in anothermodification, to enter a pair of piles comprising a pair of batter pilesor alternatively, a vertical and a batter pile, and with suflicientclearance, in each modification, that concrete may be subsequentlypoured into the space between the collar and pile or pile pair, as thecase may be.

The piles are so driven, as by means of a spotting tem plate, that afterthey are cut off to the required elevation above the water level, theirupper ends will be positioned in alignment with the respective collarsof the platform as the latter is lowered into position by means of abarge crane.

For initially securing the respective collars to the so entered pile orpile pairs, preparatory to pouring the concrete, each collar has tappedtherethrough at spaced points extending vertically and peripherallythereof, a series of bolts which are adjustable by a wrench to grip theso entered pile or pile pairs on all sides, thereby temporarily tosupport the platform on the piles. After the bolts are thus tightened,there is no relative movement between the piles and the platform frame.The space between each collar and the pile or pile pair entered thereinis then filled with concrete. The motion of the piles due to wave actionwill not disturb the setting of the concrete.

Each of the piles is then filled with a solid plug of concrete whichextends from the cut-off elevation to a point several feet below thewater surface. The top of each pile or pile pair is furnished with asteel pedestal anchored in the concrete plug, to receive the drillingfloor.

Thus the invention provides, in one of its aspects, a

simple means of connecting the superstructure to the piles.

Having thus described the invention in general terms, reference will nowbe had, for a more detailed description, to the accompanying drawings,wherein:

FIG. 1 is a view in elevation, and partly in section, of a platformsuperstructure and pile assembly, in accordance with the invention;while FIG. 2 is a plan view thereof, and FIG. 3 a sectional elevation at3-3 of FIG. 2. FIG. 4 is an enlarged plan view of one of the collar andpile assemblies of the FIGS. 1-3, inclusive, showing; while FIG. 5 is avertical section taken at 5-5 of FIG. 4. FIGS. 6 and 7 are,respectively, a plan view and a view in elevation of a collar and pileassembly, employing a pile pair consisting of a vertical pile and abatter pile assembled in the collar and secured thereto as abovedescribed. FIG. 8 is a plan view similar to FIG. 6 of anothermodification wherein a pair of batter piles are assembled in a collar ofthe superstructure.

FIGS. 9 and 10 are, respectively, views in elevation and plan, of a pileanchoring and template arrangement for adjust-ably anchoring the centeror well conductor pile head at the exact location desired, and fordriving the platform supporting piles thereabout in alignment with theplatform collars respectively, for entry therein. FIG. 11 is an enlargedview in elevation of the upper portion of FIG. 9. FIG. 12 is afragmentary detail of a winch arrangement for appropriately tensioningthe cables of the FIGS. 9-11, inclusive, anchoring assembly.

Referring to FIGS. 1-5 inclusive, the drilling foundation therein shown,comprises a steel frame superstructure 10, mounted on four prestressedconcrete, tubular or shell type piles 11-14 inclusive, of cylindricalcontour disposed about a central or well conductor pile 14a. The pilesare made up of centrifugally spun, precast concrete sections, each ofabout 16 feet in length. A plurality of longitudinally extending holesare cored at equi-spaced intervals about the circumference of the shellsas they are spun, and the shell sections are fastened together by posttensioned cables extending through the core holes, as at 15, 16, FIG. 5.The pile sections may be produced "as set forth in Us. Patents2,550,858, I. T. Parret, and 2,602,979, M. Van Buren, and joined withpost tensioned cables as described in US. Patent 2,609,586, R. M. Parry.

The piles as thus assembled are of such length that when driven into thebed 17 of a body of water 18, where drilling is to be carried out, theupper ends will extend sufficiently above the water level 19, that theymay be cut off to the required elevation, for mounting thesuperstructure 10 thereon. The steel superstructure 10 is completelyprefabricated in the land-based yard as a unitary structure, which islifted onto a barge and transported to the drill site where it is placedon the piling as described more in detail below.

As shown in FIGS. l-3 inclusive, the superstructure is of substantiallyrectangular configuration in elevation and in plan, having disposed atits respective corners, the above mentioned collars 20-23, inclusive,into which the piles 11-14 are respectively entered and secured to thesuperstructure as hereinafter explained. Extending horizontally betweenadjacent collars, such 'as 20, 23, are pairs of upper and lower channelmembers, as at 24, 25 and 26, 27, the inner faces of which are welded tothe opposite ends, respectively, of vertically extending I beams, 'as at28, 29, disposed intermediate the ends of said channel members, and toend plates disposed at the opposite ends thereof, as at 30, 31. Thevertical members function as struts, and the channels and struts arebraced against lateral and corner-to-corner deflection, by

3 additional I beams extending in oppositely inclined diagonaldirections between the upper and lower channel pairs and adjacentverticals, as at 32, 33 and 34, 35.

A series of parallel and equi-spaced I beams, as at 41, extend betweenthe oppositely disposed upper channel members 25 and 47, being welded attheir opposite ends thereto, respectively. These beams serve as flooringbeams for a steel floor grating 43 mounted thereon and secured thereto.The floor beams are in turn buttressed at intermediate points by a pairof cross or I beams 54 51, which extend beneath the floor beams, betweenthe oppositely disposed pairs of vertical beams 52, 53 and 54, 55,respectively, being welded to these verticals.

The superstructure as thus far described is additionally braced by aseries of I beams, extending diagonally beneath the floor beams, as at56, 57, from the vertical member 58, to the vertical members 52, 53,respectively, and as at 59, 60, from the vertical members 52, 53,respectively, to the midpoint of the I beam 51. In similar fashionadditional I beams extend diagonally from the midpoint of beam 50, as at61, 62, to the vertical members 54, 55, respectively, and as at 63, 64,from these members, respectively, to the vertical member 65.

Diagonal bracing for the lower part of the superstructure, is providedby pipe sections, as at 7 -73 inclusive, which extend, respectively,etween the midpoints of adjacent lower channel members, being welded tothereat, as more particularly shown in FIG. 3, for pipe sections 70, 71,terminating at the inner lower channel members 27 and 74, respectively.

The trussing of the superstructure is thus such that the entirestructure acts as a portal frame when subjected to design loads.

The well conductor pile 14a extends through the framework of thesuperstructure in the manner shown in FIGS. 1 and 2, and is accessiblethrough an opening 3%} in the floor grating 48. It is braced at itsupper end, by means of a clamping ring 81, from which tie rods, as at82, 83, equipped with turnbuckles, as at 84, extend to the I beams 50,51, being appropriately secured to each. The flooring area around thewell conductor pipe is strengthened by additional flooring I beams as at85, 86, extending between beams 50, 51, and cross beams 86a, 87,extending between beams 85, 36.

The superstructure includes a landing platform 30 carried by the lowerportion of the framework and equipped with a boat fender system 91 oftimbers, and also a barge fender system 92, also mounting fendingtimbers 93. A stairway 94 extends from the upper grating 48 to the lowergrating 95 of the landing platforms. The construction of these itemsbeing conventional, requires no detailed description.

FIGS. 4 and 5 are illustrative of the corner mounting of the FIGS. l-3,inclusive, superstructure on each of the piles 11-14 inclusive. It willbe observed from these views that the collar A which is typical of anyof the collars 20-23 inclusive, of FIG. 1, is substantially in the formof an oval-shaped tube, i.e., oval in plan view as in FIG. 4, with thewall portion parallel to the axis of the tube, as in FIG. 5. The collarhas formed integral with or welded to its outer surface at equi-spacedintervals, strengthening ribs or flanges, as at 100.

As further shown in these views, the sectional dimensions of the collarA, are substantially greater than that of the pile B entered therein,and such as to provide ample space between the two on all sides forplugging with concrete, as at 101. For example, for accommodating a pileof 54" in diameter, appropriate dimensions for the collar would be 6'9for the longer axis, 5'6" for the shorter axis, and the height 7'2.

Tapped through the collar at vertically and circumferentially spacedintervals, are a series of threaded bolts, as at 102-105, inclusive,provided with nut heads, as at 106, for adjusting with a manually orpower actuated wrench, and lock nuts, as at 107, for locking the boltsin any desired position of adjustment.

Reverting to FIGS. 1-3, as was above explained, when the piles 1 1-1 4inclusive, have been driven to the desired depth and cut oil to thedesired elevation above the water level, the superstructure 10 islowered into position, with the collars 20-23 inclusive, aligned withthe tops of the piles 1.1-1.4 inclusive, respectively, and the pilesentered therein. At this stage the bolts 102-105, inclusive, FIGS. 4 and5 are adjusted substantially to their outermost positions to provideample clearance for entry of the pile heads into their respectivecollars to the extent shown in FIG. 5. The bolts are then adjustedinwardly until they grip the pile head on all sides in the mannerillustrated in this figure, thus temporarily to support thesuperstructure 14) in the pile heads in the relative positions shown inFIG. 1. The space between each collar and pile is then filled withliquid concrete, as at 101, FIG. 5, for which purpose a temporaryretaining ring is placed around the pile to close 011 the openingbetween the pile and the base of the collar, as at 108, FIG. 5, whichmay be done either before or after the pile has been entered into thecollar. During the setting of the concrete, the bolts 102- 105,inclusive, grip the pile head with sutficient firmness that the motionof the piles due to wave action will not disturb the setting.

Each pile is also filled with a solid plug of liquid concrete whichextends from the out 01f elevation to a point several =feet below thewater level, as at 109, FIGS. 1 and 5. To retain the concrete plugduring pouring and setting, a disc of wood or the like is initiallythrust into the pile cavity to the desired depth and held by friction,as at 110, FIG. 1.

While the concrete of the plug is still liqu-id, the tubular base 111,FIG. 5, of a steel pedestal 112, is thrust into it to support on eachpile head, a drilling fioor, as at 113, FIG. 1, for drilling floor 114.

Referring to FIGS. 9-12, inclusive, there is shown a suitable type oftemplate and anchor line assembly for accurately spotting and drivingthe batter piles 11-13, inclusive, in relation to the well conductorpile 14a. The template shown generally at 115, comprises a centralsleeve member 116 integral with a cap member 116a terminating in alifting eye 116b, which assembly is sleeved over the upper end of thewell pile 14a and retained by the cap 116a in the position shown in FIG.11. To the sleeve member 116, there is pivotally attached, as at 117, aseries of four radially extending arms, as at 1 18, terminating at theirouter extremities in arcuately shaped guide members 119, adapted toengage and guide the batter piles 11-13, inclusive, during driving inthe manner shown in FIG. 11.

During driving the arms 118 are maintained in the elevated positionshown, by cables 112i), equipped with tumbuckles 121, which extendbetween the guide members 119 and an upper portion of the sleeve 116, asat 121. When the driving is complete, the cables 120 are released, sothat the arms can be folded down in the direction of the arrows X, andthus clear the batter piles in order to permit removal of the templateby the crane cable 1 16c attached to the lifting eye.

In order to pull the top of the center pile 14a, to exact location atthe water level, if necessary, preparatory to driving the batter piles11-13, inclusive, anchor lines, as at 125, may be utilized, which extendfrom small hand or power driven winches, as at 126, mounted on thesleeve member 116, thence to anchors, as at 127, embedded in the waterbed 17. By appropriately actuating the winches 126, the center pile maybe adjusted at the water level to the exact location desired, and heldthere by the anchor lines during driving of the batter piles.

FIGS. 6 and 7 show a modification of the invention wherein thesuperstructure 10 of FIGS. 1-3 is supported at each of its four cornerson a pair of piles, comprising a plumb or vertical pile 1 30 and abatter pile 131. For this purpose a modified type of collar is requiredfor mounting on the superstructure. The modified collar,

shown at C, has substantially the contour in elevation of the numeral 8,the side walls being intended at the middle of the longer axis, as at132, 133, and having Welded thereto at equi-spaced intervals vertically,a series of strengthening ribs or flanges, as at 134-, which follow thecontour of the collar along their inner edges, but have rectilinearouter edges spanning, as at 135, 136, the indented collar portions.Tapped through the collar at spaced points vertically are a series ofadjusting bolts, as at 137-146, inclusive, like those of the FIGS. 4 and5 embodiment.

After the pile pairs are driven and cut off to the proper elevationabove the water level as above described, the superstructure mountingthe collars C, is lowered into position to enter the pile pairs in thecollars respectively, in the manner shown. The bolts are then tightenedagm'nst the piles 130', 131.

In this modification, the purpose of imparting the numeral 8configuration to the collars, is to permit the adjusting bolts to gripeach pile over a suflicient circumferential extent of each to hold bothfirmly in position until the concrete has been poured and set. Thus itwill be noted that bolts 140444 grip pile 1 31 on all sides, while theremaining bolts similarly grip pile 130. The straight outer edges v135,136 of the flanges 134, prevent the indented portions 132, 133 of thecollars from being pulled away from the piles.

When the bolts have been thus adjusted, the space between the piles andcollars is filled with liquid concrete as previously described. Also thepiles are filled with plugs of liquid concrete as above described inwhich are embedded the tubular bases of steel pedestals, such as 147',to receive the drilling floor as previously described.

The collar construction of FIG. 8 is generally like that of FIGS. 6 and7 except for being adapted to receive a pair of batter piles instead ofone plumb and one batter pile. The collar D is of the numeral 8 contourin plan and braced by flanged ribs as at 150, the inner edges of whichfollow the collar contour indentations, as at 1, 152, but which haverectilinear outer edges spanning these indentations, as at 153, 154, forreasons above explained. It will be seen that the two sets of adjustingbolts, 155, 156, grip the piles 157, 158 circumierentially thereabout ineach instance.

What is claimed is:

1. The method of erecting an offshore structure consisting of a unitaryplatform mounted on pile ends by means of metal collars integral withsaid platform and of substantially greater transverse dimensions thansaid pile ends, said collars having adjusting bolts tapped therethroughat spaced points thereabout, said method comprising: driving said pilesat spaced intervals such that their upper ends may be entered into saidplatform collars,

respectively, lowering said platform into a position such that said pileends are so entered into the respective collars, maintaining theplatform so positioned while adjusting the bolts of each collar to gripon all sides the V pile entered therein, and filling the space betweeneach.

collar and pile end with liquid concrete and allowing the concrete toharden and set.

2. The method of mounting a drilling platform of unitary and rigidconstruction for oifshore oil drilling and the like, said platformhaving integral therewith at points spaced about its periphery, aplurality of metal collars disposed substantially perpendicular to saidplatform and adapted to receive the upper ends, respectively, of aseries of supporting piles of substantially smaller transversedimensions than said collars, each collar having tapped therethrough atspaced intervals, a series of bolts, threadedly adjustable tofrictionally engage a pile end entered within said collar for securingthe platform thereto and supporting the same thereat, said methodcomprising:

driving a series of piles at spaced intervals such that their .upperends may be entered into said platform collars,

respectively, lowering said platform into a position such that said pileends are so entered into the respective collars and maintaining theplatform so positioned while adjusting the bolts of each collar to gripthe pile entered therein, filling the space between each collar and pilewith liquid concrete, and allowing the same to harden and set.

References Cited in the file of this patent UNITED STATES PATENTS1,284,565 Bennet Nov. 12, 1918 1,585,254 Lund May 18, 1926 1,617,762Kiefer Feb. 15, 1927 1,807,962 Cassiere June 2, 1931 2,429,952 WilleyOct. 28, 1947 2,589,146 Samuelson Mar. 11, 1952 2,592,448 McMenimen Apr.8, 1952 2,651,181 Alcom et al. Sept. 8, 1953 2,653,451 McCullough Sept.29, 1953 2,667,038 Bayley Jan. 26, 1954 2,736,172 McChesney Feb. 28,1956 2,775,095 Harris Dec. 25, 1956 2,775,869 Pointer Jan. 1, 19572,822,670 Suderow Feb. 11, 1958 2,933,898 Upson Apr. 26, 1960 FOREIGNPATENTS 2,228 Great Britain June 27, 1873 OTHER REFERENCES CivilEngineering, pp. 41-43, July 1956.

Reprint of Civil Engineering magazine article, July 1956, PrestressedPrecast Platform Built in Gulf, Robert N. Bruce, Jr.

1. THE METHOD OF ERECTING AN OFFSHORE STRUCTURE CONSISTING OF A UNITARYPLATFORM MOUNTED ON PILE ENDS BY MEANS OF METAL COLLARS INTEGRAL WITHSAID PLATFORM AND OF SUBSTANTIALLY GREATER TRANSVERSE DIMENSIONS THANSAID PILE ENDS, SAID COLLARS HAVING ADJUSTING BOLTS TAPPED THERETHROUGHAT SPACED POINTS THEREABOUT, SAID METHOD COMPRISING: DRIVING SAID PILESAT SPACED INTERVALS SUCH THAT THEIR UPPER ENDS MAY BE ENTERED INTO SAIDPLATFORM COLLARS, RESPECTIVELY, LOWERING SAID PLATFORM INTO A POSITIONSUCH THAT SAID PILE ENDS ARE SO ENTERED INTO THE RESPECTIVE COLLARS,MAINTAINING THE PLATFORM SO POSITIONED WHILE ADJUSTING THE BOLTS OF EACHCOLLAR TO GRIP ON ALL SIDES THE PILE ENTERED THEREIN, AND FILLING THESPACE BETWEEN EACH COLLAR AND PILE END WITH LIQUID CONCRETE AND ALLOWINGTHE CONCRETE TO HARDEN AND SET.